Nitrogen dosed base

ABSTRACT

A container base that is capable of withstanding an internal pressure and further capable of causing an even deflection, such as that created by introducing liquefied gas during a hot filling process. The base includes a heel with a standing ring disposed at a lower portion thereon. A generally concave push up portion extends radially inward from the standing ring portion. At least two reinforcing rings are disposed on the push up portion, wherein the reinforcing rings diminish uneven deflection to prevent the container from tipping while resting on a flat surface.

FIELD OF THE INVENTION

The present invention relates to plastic containers, and moreparticularly to plastic containers capable of receiving positiveinternal pressure.

BACKGROUND OF THE INVENTION

Plastic containers have been replacing metal and glass containers withincreasing frequency due to the many advantages that plastic provides.The safety and appeal of plastic containers have been enhanced furtherby the development of hot filling processes, in which a product isintroduced into the container at an elevated temperature and thenimmediately sealed. By hot filling, such products are adequatelysterilized.

When a beverage or product is hot filled, however, the beveragetemperature imposes mechanical stresses on the container's structure.For example, as the hot-filled liquid cools, it decreases in volumewhich has the effect of producing a negative pressure in the container.As a result, the hot filled containers deform, affecting theiraesthetics. Accordingly, hot filling capabilities have spurred thedevelopment of related technologies to address problems of containerdeformation.

One approach to counteract negative internal pressure from a hot fillingapplication is employing vacuum panels or other structures that flex ordeform. Multiple designs and approaches to vacuum panels in thecontainer sidewalls have been developed. For example, some designsprovide ribs to increase hoop stiffness and eliminate bulges whileintegral vacuum panels collapse inwardly.

Furthermore, bases for hot filled containers have been developed thatare capable of withstanding internal negative pressures. Typically, thebases contain a continuous standing ring and a ribbed recess portion. Inorder to promote flexing or deformation, the standing rings are usuallyquite large and substantially flat in order to accommodate the internalnegative pressure. The ribs of the container bases generally areconfigured to control only inwardly directed forces and deformation.

Another approach to prevent deformation is called nitrogen dosing.Liquid nitrogen will expand to its gas form when released into theatmosphere. The actual volume of the gas is many times greater than thevolume in its liquid state. Therefore, if a small amount of liquidnitrogen is placed in the headspace of a container just before thecapping point, the liquid will still be expanding once the lid issealed. As the liquid changes to gas, its volume will increase, which tosome extent counteracts the negative pressure induced by the decrease ofthe hot filled contents upon cooling. U.S. Pat. No. 5,251,424 (Zenger),generally describes nitrogen dosing for hot fill bottles, but such amethod has not been widely commercialized.

It is a goal of the present invention to provide a base, andcorresponding container, that is capable of withstanding positiveinternal pressure and reducing deflection as a result of nitrogendosing.

SUMMARY OF THE INVENTION

A base is provided for a container that is suitable for withstandinginternal pressurization and reducing deflection as a result of nitrogendosing. The bottle may be used for hot filling or filling at ambienttemperatures. The base includes a heel, a standing ring, a push upportion, and a plurality of ribs. The heel is curved in transverse crosssection. The standing ring is located at the lower portion of the heeland includes circumferentially spaced apart contact portions that aregenerally arcuate in transverse cross. The push-up portion generally isconcave and extends radially inward from the standing ring portion. Thepush-up portion includes a gate area, a first circular reinforcing ringand a second circular reinforcing ring. Finally, a plurality of ribsextend radially outwardly from the gate portion, through the first andsecond reinforcing rings and through the standing ring.

The base geometry preferably does not contain any flat area, to reducethe deflection as a result of nitrogen dosing. The base geometry isdesigned to sag down, but not touch the standing surface. Thereinforcing ribs incorporated at the base, contain and diminish unevendeflection so that the bottle doesn't tilt to one side. Accordingly, abase capable of withstanding internal positive pressure and diminishinguneven deflection as a result of nitrogen dosing is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an embodiment of a container illustratingaspects of the present invention;

FIG. 2 is a bottom view of the container shown in FIG. 1;

FIG. 3 is a cross sectional view of the container shown in FIG. 1; and

FIG. 4 is a cross sectional view of a portion of the rib taken throughline 4-4 of FIG. 2.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

A container 10 is capable of withstanding internal positive pressure. Ina preferred embodiment container 10 generally includes a neck 12, a body16, and a base 20. Neck 12 extends downward into body 16 and base 20extends downward from a lower portion of body 16. Neck 12 generally is arigid ring adapted to receive and withstand the mechanical loads imposedby a threaded closure (Not shown). Body 16 can be formed into a myriadof configurations to provide the desired structural characteristics,aesthetic qualities, and product identification. Generally, neck 12 andbody 16 may be of any design.

Base 20 generally includes a heel 24, a standing ring 26, a push-upportion 28 and a plural ribs 30. Heel 24 generally is curved intransverse cross section and extends downwardly from body 16 mergingsmoothly into standing ring 26. Preferably there are no flat surfaces inthe standing ring area. Standing ring 26 may include circumferentiallyspaced apart contact portions 34. Contact portions 34 are generallyarcuate in transverse cross. Container 10, generally rests on contactportions 34 while in an upright position.

Push-up portion 28 is generally concave and extends radially inward fromstanding ring 26. Push-up portion 28 contains a gate area 40, a firstreinforcing ring 43, and a second reinforcing ring 47. Gate area 40preferably is disposed at the center of push-up portion 28. Gate area 40preferably includes a recess 60 located substantially at the center ofgate 40 for receiving a preform's gate during blow molding. Gate area 40may also include a depression 62 formed by pinning a portion of gatearea 40 between the distal ends of a stretch rod and a mold. Secondreinforcing ring 47 is substantially circular and disposed proximatestanding ring 26. First reinforcing ring 43 is also substantiallycircular and disposed between gate area 40 and second reinforcing ring47. Preferably, reinforcing rings 43 and 47 are generally concave,however, they are not limited to such a design.

Ribs 30 generally extend radially outward from gate area 40, throughfirst reinforcing ring 43, through second reinforcing ring 47, andthrough standing ring 26. Ribs 30 preferably are concave and contain atrough 52 over at least a portion of its radial length, wherein trough52 preferably has an upper rib surface 56. Preferably, upper surface 56is substantially flat, however, is not limited to such a design.Preferably, base 20 has six ribs 30 and six contact portions 34,however, the design is not limited to such a configuration and maychange depending on the size of the container.

Container 10 having base 20 as described herein is intended to be filledat an elevated temperature, and base 20 is configured to receivecontents at up to approximately 212 degrees F. without failure, althoughsuch temperature is not a limit to the scope of the invention. In thisregard, a plastic resin preferably having an intrinsic viscosity of overapproximately 0.75 may be employed, more preferably over approximately0.80, and most preferably approximately 0.84 may be employed. Thepresent invention is not limited to such viscosities, which are providedonly for guidance.

Upon introduction of the contents into container 10, a predeterminedquantity of liquefied gas is introduced therein. The liquefied gas,which preferably is liquefied nitrogen, quickly vaporizes. Aftercapping, the vaporization increases the internal pressure withincontainer 10. Preferably, the internal pressure range is 15 to 35 psi athot-fill temperature, and 0-10 psi upon cooling to ambient temperature(approximately 72 degrees). The pressure ranges are provided to beexemplary, and the scope of the present invention is not limited to suchpressure ranges.

Techniques for introducing liquefied gas into container 10 are wellknown, especially by persons familiar with such technology forintroducing liquefied nitrogen into metal cans. Such nitrogen dosingsystems are commercially available and nearly exhaustively described inthe literature. The present invention is not limited to a particularmeans for introducing liquefied gas, but rather encompasses anyintroduction technology. The magnitude of the dose of liquefied gasintroduced into the container may be determined according to suchparameters as contents temperature, headspace volume, characteristics ofthe container (including its elasticity or relationship between volumechange and pressure), order of introduction of the product and nitrogendose (that is, whether the nitrogen dose is introducing into thecontainer before, concurrently with, or after the contents), and thetime period between introducing the nitrogen dose and capping orsealing. Choosing the magnitude of the dose of liquefied gas for aparticular application will be straightforward for persons familiar withliquefied gas dosing technology, such as, for example, as used in themetal can industry, in light of the present disclosure and the aboveparameters.

The internal positive pressure within container 10 acts on all surfacesof base 20. Thus, pressure urges push-up portion 28 substantiallydownwardly, urges against the interior surfaces of ribs 30 substantiallydownwardly and substantially inwardly, urges against the interiorsurface of standing ring 26 substantially downwardly, urges against theinterior of heel 24 substantially outwardly and somewhat downwardly, andin particular urges against the interior surface of the area betweenreinforcing rings 43 and 47 substantially downwardly. Each of thedownward components of the pressure vectors, as well as most of theother components of the pressure vectors, urges base 20 towardinversion. The term “substantially downwardly” as used herein refersgenerally to the downward direction when the container is upright, andmay also include a lateral component.

Conventional bases often fail under such conditions either by completeinversion, which is a complete failure mode in which much of push-upportion 28 is pushed fully out the bottom of base 20 to break the planedefined by standing ring 26, or by partial inversion, in which a portionof standing ring 26 (most often a single circumferential location) ispushed downwardly relative to the plane defined by the as-moldedstanding ring. Even a partial inversion of small magnitude might destroyor inhibit the container's ability to solidly rest on a flat surface.

To withstand this positive internal pressure, a draft surface connectedto the standing ring has been utilized. The draft surface deformssubstantially downwardly in response to the internal pressurization ofthe container. The container is then still able to rest on the standingring even after the internal pressurization. Unfortunately, the deformeddraft surfaces can deform unevenly thereby causing the bottle to tilt.

In the present embodiment standing ring 26 is stiffened by ribs 30,thereby diminishing downward deflection of standing ring 26, uponpressurization of base 20, compared with an unstiffened configuration.Reinforcing rings 43 and 47 contain and cause an even deflection insubstantially a downward direction, thereby preventing the bottle fromtilting once pressurized. Also, the base geometry preferably does notcontain any flat area, to help reduce such deflection. Thus, standingring 26, ribs 30, and reinforcing rings 43 and 47 each enhance thestability of container 10 when standing upright on standing ring 26 andhelp contain and cause an even deflection.

Preferably, base 20 in its fully deformed or deflected state, does notinterfere with standing ring 26 such that standing ring 26 remainscircumferentially continuous. In this regard the deflected surfaces donot extend downwardly below standing ring 26 even in its deformed ordeflected state such that substantially all of standing ring 26 issubstantially planar.

Persons familiar with preform and blow molding processes and technologyin light of the present disclosure will be enabled to configure acontainer that employs the present invention(s). Preferably, to enhancethe ability of the bottle to remain vertical without listing underinternal pressure, the gate is pinned to the center and does notdeviate. Furthermore, it is preferable that the material is evenlydistributed around the base to obtain the full benefits of theinvention. Accordingly, pinning the gate at the center and providing aneven material distribution, results in an even height increase and thebottle will not tilt while under pressure.

Container 10 may be formed of conventional plastics suitable for coldfilling, such as commonly used for water or like, non-carbonatedbeverages. Container 10 may also be formed of conventional thermoplasticsuitable for conventional hot-filling. Persons familiar with containerengineering in light of the present disclosure will be able to engineera container by choosing parameters (such as polymer choice, intrinsicviscosity, blow molding or other forming techniques, and the like) so asto practice each aspect of the invention disclosed herein.

The present invention is illustrated in the particular embodimentdescribed above. The invention, however, is not limited to thisembodiment, but rather encompasses structure and the related function asdefined in the claims. For example, the structure of the bottle hasadvantages for use with positive internal pressure, but the presentinvention is intended to be limited to positive internal pressureapplications unless expressly recited in the claims.

1. A plastic bottle suitable for containing a non-carbonized beverage,said bottle comprising: a body and a neck that terminates in a finish;an enclosed based extending from a lower portion of the body, said basecomprising: a heel that is curved in transverse cross section; astanding ring portion disposed at a lower portion of the heel, thestanding ring portion includes circumferentially spaced apart contactportions, each one of the contact portions being generally arcuate intransverse cross, the bottle resting on the contact portion whileupright; a generally concave push-up portion extending radially inwardlyfrom the standing ring portion, the push-up portion including: (i) agate area substantially at a center thereof, (ii) a first substantiallycircular reinforcing ring disposed proximate the standing ring portion,and (iii) a second substantially circular reinforcing ring disposedbetween the gate area and the first reinforcing ring; and plural ribsextending radially outwardly from the gate portion, through the firstand second reinforcing rings, and through the standing ring, whereby thereinforcing rings contain deflection and diminish uneven deflection ofthe base in response to positive internal pressure.
 2. The bottle ofclaim 1 wherein the base resists inversion by uniformly transmittingforces to the contact portion of the standing ring.
 3. The bottle ofclaim 1 wherein the first reinforcing ring and the second reinforcingring are generally concave.
 4. The bottle of claim 1 wherein the gatearea includes a recess in the center thereof for receiving a preform'sgate during blow molding.
 5. The bottle of claim 1 wherein the gate areaincludes a depression formed by pinning a portion of the gate areabetween a distal end of a stretch rod and a mold.
 6. The bottle of claim1 wherein the rib has a substantially flat trough over at least aportion of its radial length.
 7. The bottle of claim 6 wherein thetrough is substantially flat over most of the radial length of the rib.8. The bottle of claim 1 wherein each surface of the standing ring isarcuate in transverse cross section.
 9. The bottle of claim 1 whereineach surface of the push-up portion is arcuate in transverse crosssection.
 10. The bottle of claim 1 wherein the quantity of contactportions is at least six and the quantity of ribs is at least six.
 11. Amethod of filling a plastic container comprising the steps of: (a)providing a container that includes: a body and a neck that terminatesin a finish; an enclosed based extending from a lower portion of thebody, said base comprising: a heel that is curved in transverse crosssection; a standing ring portion disposed at a lower portion of theheel, the standing ring portion includes circumferentially spaced apartcontact portions, each one of the contact portions being generallyarcuate in transverse cross, the bottle resting on the contact portionwhile upright; a generally concave push-up portion extending radiallyinwardly from the standing ring portion, the push-up portion including:(i) a gate area substantially at a center thereof, (ii) a firstsubstantially circular reinforcing ring disposed proximate the standingring portion, and (iii) a second substantially circular reinforcing ringdisposed between the gate area and the first reinforcing ring; andplural ribs extending radially outwardly from the gate portion, throughthe first and second reinforcing rings, and through the standing ring;(b) introducing a liquid into the container; (c) introducing a liquefiedgas into the container; and (d) capping or sealing the container afterthe introducing steps (b) and (c); whereby the reinforcing rings containdeflection and diminish uneven deflection of the base in response topositive internal pressure.
 12. The method of claim 11 wherein the stepof introducing the liquid includes introducing the liquid at an elevatedtemperature.
 13. The method of claim 11 wherein the step of introducingthe liquid includes introducing the liquid approximately at ambienttemperature.
 14. The method of claim 11 wherein the base resistsinversion by uniformly transmitting forces to the contact portion of thestanding ring.
 15. The method of claim 11 wherein the gate area includesa recess in the center thereof for receiving a preform's gate duringblow molding.
 16. The method of claim 11 wherein the gate area includesa depression formed by pinning a portion of the gate area between adistal end of a stretch rod and a mold.
 17. The method of claim 11wherein the rib has a substantially flat trough over at least a portionof its radial length.
 18. The method of claim 17 wherein the trough issubstantially flat over most of the radial length of the rib.
 19. Themethod of claim 11 wherein each surface of the standing ring is arcuatein transverse cross section.
 20. The method of claim 11 wherein eachsurface of the push-up portion is arcuate in transverse cross section.